The present application is related to the following applications.
The aforementioned applications and patents are commonly assigned with the present invention and are incorporated herein by reference.
The present invention is directed, in general, to packaging for electronic components and, more specifically, to a multifunction lead frame and an IC package incorporating the lead frame for both lead and internal component purposes.
Power supplies and especially power converters are becoming increasingly important elements of systems in the telecommunications and computer-related fields. In conjunction therewith, the power converters require increased power densities, which relate a power output capability to the size of the power unit. Typically, power converters include a combination of integrated circuits (ICs) and discrete components.
The packaging of the power units continues to be a challenging area due to the desired power densities in view of, for instance, the thermal limitations associated with packaging more power in a smaller package. Previous efforts to create monolithic-like power processing modules have been relegated to packaging discrete components into a single integrated package. The resulting packages suffer from a number of shortcomings as hereinafter described.
Since discrete components are generally prepackaged in a variety of preselected component sizes, sizable printed wiring boards (PWBs) or substrates are necessary to accommodate the components and to make the interconnections therebetween. This detracts from the power density of the power unit due, in pertinent part, to a loss of space efficiency. Additionally, there is usually an increased incremental cost associated with using prepackaged discrete components, since many of the current packaging strategies are based on ICs. Therefore, the use of prepackaged discrete components represents the use of xe2x80x9cpiece partsxe2x80x9d in a primarily IC environment.
As a result, current packaging schemes are directed to packaging styles, weights, sizes and configurations that are standardized around IC units. To accommodate such designs, however, irregularly shaped components are often necessary thereby adding to the cost and complexity of designing and producing packaged units.
Additionally, a circuit performance problem may arise when using prepackaged discrete components. Since the spacing between prepackaged discrete components is typically larger than the spacing between ICs, parasitic inductance and capacitance becomes a factor in the response capability of the higher frequency circuits. This may adversely impact the design of the power unit as additional components may be necessary to compensate for the parasitic elements mentioned above.
Accordingly, what is needed in the art is a more effective system and method of packaging discrete components or ICs applicable in any environment.
To address the above-discussed deficiencies of the prior art, the present invention provides a lead frame for use in packaging a circuit having a discrete component, and a method of manufacture thereof. In one embodiment of the present invention and with reference to FIGS. 1A and 1B, the lead frame 100 includes (1) a lead support structure 105, and (2) a plurality of severable leads 110 coupled to the lead support structure 105 that extend inward therefrom to predetermined locations corresponding to terminals of the discrete component.
The present invention introduces, in one aspect, the broad concept of employing a lead frame to package a discrete component, which may be used in cooperation with another discrete component attached to the lead frame. Alternately, the discrete component may be coupled to an IC attached to the lead frame. The discrete component can be selected from the group consisting of, for instance, a power switch, a capacitor, an inductor and a transformer. Of course, other discrete components are acceptable as dictated by design requirements. This approach allows pertinent components to be attached to the lead frame thereby increasing the utility of the lead frame and lowering the overall cost associated with packaging the components. This approach also extends and enhances overall modularity, which provides a generally improved flexibility of design. In summary, extending the use of the lead frame to include the coupling, for instance, of discrete components, ICs, and magnetic elements in the forming of circuits, extends and enhances the ability to increase power densities, systemize packaging strategies and lower costs.
In one embodiment of the present invention, the circuit includes an IC and the lead frame includes a second plurality of severable leads coupled to the lead support structure. The second plurality of severable leads extends inward to predetermined locations corresponding to terminals of the IC. Additionally, the lead frame may include material that is bendable. This structure facilitates direct connection of discrete components to the IC. Also, the lead support structure may form a periphery of the lead frame, although alternative designs are well within the broad scope of the invention.
In one embodiment of the present invention, the discrete component is a magnetic device having a magnetic core and the lead frame includes a severable lead having a circinate portion that forms a winding of the magnetic device. A circinate winding structure consists of a flat coil of conductor. In one embodiment, each loop of the conductor forms one turn of the winding for the magnetic device. In an embodiment to be illustrated and described, the winding consists of four circinate loops that are rectilinear. Of course, a plurality of circinate windings may interact with a magnetic core to form a magnetic device such as a transformer. The present invention is not limited to a circinate winding structure and other lead frame winding structures are well within the broad scope of the present invention.
In one embodiment of the present invention, the circuit is a power converter. The power converter includes an IC containing a converter controller and discrete power processing components coupled to the IC. Additionally, a plurality of leads are coupled to corresponding terminals of the IC and the discrete power processing components. This embodiment preferably includes a body that encloses the IC, the discrete power processing components and a central portion of each of the plurality of leads. A peripheral portion of each of the plurality of leads extends outward from the body. Additionally, while the body may be composed of a dielectric material, other materials are equally applicable as needed.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.